Despite your preference for Intel, you might want to consider an AMD 780G board. The Gigabyte GA-MA78GM-S2H seems the most popular implementation of this chipset and costs $85 to 100. The integrated graphics are excellent and can enable smooth HD video playback with a sub-$100 cpu. Speaking of which, the Athlon X2 4600+ (2.4 GHz) costs $66 on Newegg; the Athlon X2 4850e (2.5 GHz, low 45 W power) $90. Otherwise, if you don't want integrated graphics or AMD, I expect most folks will recommend the Gigabyte GA-P35-DS3L and perhaps the new Abit IP35P. They're not 100 per cent reliable, though they've got as high a rating as you can expect for a sub-$100 board.
Are you sure about Windows 2000? I mean, I ran Windows 2000 Professional on my now-retiring workstation for five years, but there are a lot of inconveniences running Windows 2000 these days. I did skip XP for Vista x64 on my new Wolfdale, despite the hate, heh. I'm not sure I'd be altogether comfortable running Windows 2000 on a system regularly exposed to the Web.